The invention relates to a for producing Peltier modules located between two substrates and to a Peltier module produced therefrom.
The production of Peltier modules according to the process which has been conventional to date is complex. Furthermore these Peltier modules do not have optimum thermal properties.
Producing the metal coating required for producing printed conductors, terminals, etc on a ceramic, for example on an aluminum oxide ceramic layer, using the so-called DCB (direct copper bond technology) process, specifically using metal or copper foils or metal or copper sheets which form the metal coating and which have on their surface sides a layer or a coating (fused layer) of a chemical compound of a metal and a reactive gas, preferably oxygen, is known. In this process which is described for example in U.S. Pat. No. 3,744,120 or in DP-PS 23 19 854, this layer or this coating (fused layer) forms a eutectic with a melting point below the melting point of the metal (for example, copper) so that by placing the foil on the ceramic and by heating all the layers they can be joined to one another by fusing the metal or the copper essentially only in the region of the fused layer or oxide layer.
This DCB process then has for example the following process steps:                oxidation of a copper foil such that a uniform layer of copper oxide results;        placing the copper foil on the ceramic layer;        heating the combination to a process temperature between roughly 1025 to 1083° C., for example to roughly 1071° C.;        cooling to room temperature.        
Furthermore, the so-called active solder process (DE 22 13 115; EP-A-153 618) for joining metal layers or metal foils which form the metal coatings, especially also copper layers or copper foils to the respective ceramic material, is known. In this process which is used especially also to produce metal ceramic substrates, at a temperature between roughly 800-1000° C. a connection between a metal foil, for example copper foil, and a ceramic substrate, for example aluminum nitride ceramic, is produced using a brazing solder which in addition to the main component, such as copper, silver, and/or gold, also contains an active metal. This active metal, which is for example at least one element of the group Hf, Ti, Zr, Nb, Ce, by a chemical reaction produces a connection between the solder and the ceramic, while the connection between the solder and the metal is a metallic brazing solder connection.
It is an object of the invention is to devise a process with which simplified production of Peltier modules is possible.